1. Field of the Invention
The present invention relates generally to a cascaded base station and, more particularly, to a cascaded base station and an operation method thereof for connecting a plurality of sub-base stations and a plurality of Remote Radio Units (RRUs) via a radio resource expansion device in a cascaded manner so as to operate as a single base station in a time domain and share the RRUs having respective cells.
2. Description of the Related Art
Cellular system base stations are typically deployed independently. Accordingly, an increase in the number of RRUs for cell coverage expansion is limited. FIG. 1 is a diagram illustrating a configuration of a conventional base station. FIG. 1 is directed to the conventional base station with three sectors and six Frequency Assignments (FAs). Typically, an n-sector base station is provided with n RRUs.
FIG. 2A is a diagram illustrating a hexagonal topology of the conventional cellular system, and FIG. 2B is a diagram illustrating an enlarged view of a cell of the hexagonal cellular system of FIG. 2A. As shown in FIG. 2B, a cell is divided into three sectors with FAs. Referring to FIG. 2A, a mobile communication network is composed of a plurality of cells controlled by respective base stations. FIG. 2B is directed to a cell divided into 3 sectors using multiple FAs.
As shown in FIGS. 1, 2A, and 2B, a conventional base station is implemented separate from other base stations. In the case of a cellular mobile communication network composed of a plurality of base stations, each base station has a relatively small cell coverage, such that users on the move cross cell boundaries. Whenever a user crosses a cell boundary, a handover (e.g. soft handover) occurs. However, if the handover occurs frequently, the base stations must prepare for the handover by allocating necessary resources, resulting in unnecessary resource waste and data service restriction. Furthermore, in the conventional system, the throughput per Packet Data Service (PS) decreases as the required subscriber accommodation capacity increases.